In cinematography, it is common practice to join film sections by splicing. During cinematographic shooting a series of scenes is filmed onto the same negative film. From this negative film, a positive film is printed that allows these various scenes to be viewed and those that will make up the final cinematographic work to be selected. When this selection has been made, the final version of the cinematographic work is produced by cutting and splicing together the negative film according to the selected scenes.
In the first place, the negative film is cut. This cut can be done using a straight cutter which at the same time removes the emulsion layers from the part of the film to be spliced. It can also be done using a chamfer cutter, which chamfers the ends of the films to be spliced in a complementary way. Then this part of the film is glued, and this glued part is assembled with the end of the film to be spliced by maintaining pressure until the films are finally spliced. To increase the speed of splicing, a splicing technique called "hot splicing" consists in carrying out the splice at temperatures that can reach 50.degree. C.
This splicing is especially tricky to use because the negative film resulting from the splicing of the film parts is the base film that will be used to produce copies for projection on a film screen. Thus the splices must be solid to withstand the mechanical stresses that the film is subjected to when printing the copies. Further these splices must withstand cleaning of the film in solvents. After splicing the film, it is essential to remove the traces of the glue remaining on the film. Finally, these splices must not be photographically visible because they would be reproduced on the copies obtained from this film.
Glues containing nitrocellulose in solution in a mixture of organic solvents are known for splicing photographic films. These glues contain solvents of the dioxane and/or dichloromethane or dichloroethane type in substantial quantities. For safety and environmental reasons, it is desirable to use glues that do not contain these organic solvents; in particular in the hot treatment processes that help these solvents to evaporate. It is particularly desirable to have a glue that does not contain dioxane.